3100cn: Forcing paper size, tray

Hi, I have a new Dell 3100cn color laser printer. I have letter-size paper in Tray 1, nothing in the MPF.

My problem is that we get documents from around the world, some of which are designed for A4 paper which we do not support, and I want the printer to just print these documents ANYWAY, on letter-size paper. Our HP printers let us do this, but on the Dell, it just causes the printer to freeze with the message "Insert A4 Paper", and the only thing you can do is cancel the job!

I've gone into the web interface for the printer and tried to hard-code as many settings as possible to "Tray 1" and "Letter". But when I send one of these files, the printer is still saying "Insert A4 Paper."

I do NOT want to have to modify every file's source and/or modify the settings on every computer in the group to have them force the paper size. I just want the PRINTER to PRINT using the paper that's in the tray, and not give me any "lip"...